Optics plays an important part in for instance lighting technology, medicine, industrial measuring and monitoring applications and in telecommunications technology. A conventional optical system comprises macroscopic components placed widely apart from one another, and the size of a particularly complicated optical system may fill even a cubic meter space. In integrated optics, the aim is to combine optoelectro-mechanical structures in order to reduce the size using waveguide optics, packed optics or plane integrated optics.
Integrated microtechnology often employs diffractive optics, the components thereof comprising microstructures for manipulating optical radiation as desired. A diffractive component is used for example as a lens, a beam divider, an intensity distribution modifier, a mirror, an optical safety marking, a filter, an anti-reflecting surface or a polarization modifier.
A diffractive component is used as an element in an optical coupling arrangement based on substrate waveguide and comprising a glass substrate. Diffractive elements, the optical function of which is based on changes of the refractive index within the polymer, can interferometrically be made on the surface of the substrate using holographic exposure. Another alternative is to etch and metal coat the surface of a glass substrate (or quartz substrate), in which case the optical function of the diffractive components is based on the changes made to the interface profile between glass and metal. Such elements can be used to couple optical radiation between the waveguide and the environment. Such optical coupling arrangements based on substrate waveguide are particularly suitable as a backplane of an apparatus case in telecommunications technology, as in this way the electric data transmission can be reduced within a circuit board and between circuit boards. Such a solution is described in greater detail for example in publication G. Kim, R. T. Chen, Three-dimensionally interconnected multi-bus-line bi-directional optical back-plane, society of Photo-Optical Instrumentation Engineers, Opt. Eng., 38(9), pages 1560 to 1566 and 1999, incorporated herein by reference.
A problem with the optical coupling arrangement based on substrate waveguide is that it is poorly applicable to be utilized industrially, as in order to manufacture a diffractive element the substrate must be etched and metal coated or a holographic pattern must be prepared. Such a work can only be carried out in a laboratory by hand, which in turn results in the fact that the coupling arrangement becomes very expensive, is slow to manufacture and the quality is poor due to the tolerances associated with the aligning of the parts. An extensive production to fulfil the needs of telecommunication applications for example is therefore not possible, as mass production is required in industrial applications.